A conventionally existing drug refrigerator houses and stores vaccines, drugs, samples, and the like, in an interior of a refrigerator body so as to be kept at a low temperature. In order to maintain a good storage state thereof, it is necessary to keep an interior temperature in the refrigerator body within a predetermined temperature range (see Patent Literature 1).
According to one control method for cooling the interior temperature to a predetermined temperature, if the interior preset temperature is set at 5° C., for example, control is performed in such a manner that a cooling device (including an electric compressor and a cold air circulation fan) is operated when the interior temperature is increased to the upper limit temperature set in a temperature control device whereas the cooling device is stopped when the interior temperature is decreased to the lower limit temperature set in the temperature control device, whereby the average temperature in the interior becomes equal to 5° C.
According to another control method, the cooling device is operated with an inverter control method. If the interior preset temperature is set at 5° C., control is performed in such a manner that an operation frequency of the cooling device is increased to obtain a high-speed operation state as the interior temperature is increased toward the upper limit temperature set in the temperature control device whereas the operation frequency of the cooling device is decreased to obtain a low-speed operation state as the interior temperature is decreased toward the lower limit temperature set in the temperature control device.